Rubber footwear



NOV. 2l, 1939. El W. DUNBAR 2,180,924

RUBBER FOOTWEAR Filed Feb. 24, 1957 4 Sheets-Sheet l ATTORN EY Nov. 21,1939. E, w. DUNBAR 2,180,924

RUBBER FO OTWEAR Filed Feb. 24, 1957 4 Sheets-Sheet 2 ATTORNEY Nov. 2l,1939. E w. DUNBAR RUBBER FOOTWEAR 1937 4 Sheets-Sheet 3 Filed Feb. 24

ATTORNEY Nov. 21, 1939. E w, DUNBAR 2,180,924

RUBBER FO OTWEAR Filed Feb. 24, 1957 4 Sheets-Sheet 4 Ei 15W Ufm M 24 23ATTORNEY Patented Nov. 21, 1939 UNITED STATES RUBBER FOOTWEAR Ernest W.Dunbar, Hudson, Mass., assgnor to Cambridge Rubber Co., Cambridge,Mass., a' corporationof Massachusetts e Application February 24, 1937,Serial No. 127,426

4 Claims.

'I'his invention relates to rubber soled shoes and to the parts of suchshoes. It is more especially concerned with the bottom structure offootwear of this type.

Objections often raised to the use of rubber shoes are the facts thatthey burn the bottoms of the feet of some individuals, or cause the feetto sweat excessively, and the further fact that these shoes arerelatively heavy. On the other hand, a large proportion of thepurchasing public prefers shoes with rubber bottoms because of thecushion effect which they afford, the better grip on the ground whichthey give, and their superior waterproof and wearing properties.

The present invention aims to improve rubber-soled shoes with a view toeliminating the objectionable features above mentioned, while stillpreserving the advantages of footwear of this type.

The nature of the invention will be readily understood from thefollowing description when read in connection with the accompanyingdrawings, and the novel features will be particularly pointed out in theappended claims.

1n the drawings,

Figure 1 is a perspective view of an outing or beach shoe embodyingfeatures of this invention;

Fig. 2 is a. vertical, sectional view of a portion of the sole structureof the shoe shown in Fig. 1;

Fig. 3 is a similar'view through the entire bottom of the shoe;

Fig. 4 is a transverse, sectional View through the forepart of the shoe;

Fig. 5 is a side view of a portion of the binder strip used on theoutsole;

Figs. 6 and '7 are perspective and edge views, respectively,illustrating steps in the process of manufacture of elements of the shoebottom;

Fig. 8 is an edge view showing a further step in this process;

Fig. 9 is a perspective view of a mans shoe including a bottom embodyingfeatures of this invention;

Fig. 10 is a vertical, sectional view showing a diiferent type of shoebottom embodying the invention;

Figs. 11 and 12 are perspective views of the bottom and top,respectively, of a combined sole and heel constructed in accordance withthe invention;

Figs. 13 and 14 are sectional views on the lines i3-i3 and M-H,respectively, Fig. 10;

Fig. 15 is a perspective view oi another shoe embodying this invention;

Figs. 16 and 17 are vertical, sectional views through the forepart andheel part, respectively, of the shoe shown in Fig. 15; and

Fig. 18 is a fragmentary, vertical, sectional view showing features ofanother form of the invention.

Referring rst to Figs. 1 to 4, inclusive, the shoe there shown comprisesan upper `2, an insole 3, and an outsole, which is indicated in generalat 4. The upper may be of any suitable character such as fabric,leather, or combinations of these materials. As above indicated, thegreater part of the weight of a shoe is in its bottom structure. In mostshoes it is necessary to have a bottom of considerable thickness inorder to prevent the foot from feeling too plainly the irregularities inthe ground, to provide better heat insulation, and to avoid excessiveflexibility in the shoe bottom. According to the present invention,these desirable characteristics are obtained, while still producing thenecessary wearing qualities and avoiding excessive weight, by using inthe bottom structure a high percentage of sisal fiber. In the particularshoe shown the insole 3 consists essentially of a layer of sisal ibersloosely matted together but heid in cooperative relationship to eachother through the use of a limited quan-y tity of a waterproof binder.This may, for example, be rubber. or it may consist of some celluloseester, such as cellulose acetate, dissolved in a suitable solvent. Or,binders may be dispensed with, and the body of iiber may be mechanicallybound together as, for example, by superposing a flexible top sheet a,Fig. 1, on the layer of fibers, and stitching this and said layertogether, preferably with a fabric bottom sheet.

The outsole, as shown in Fig. 3, is composed of an upper section c and alower or tread layer d. The upper section consists of a body of sisalber either made of ply structure or not, as desired, and containing asumcient proportion of rubber, or other waterproof binder, to bond thefibers securely together' but Without materially decreasing the porosityor reducing the volume of the voids in this member. The top and bottomsurfaces of this sisal fiber layer, however,

are suiciently coated with a highgrade gum covered with a binder strip 8which is initially coated with a rubber and therefore bonds securely tothe rubber content of the sisal fiber assembly.- The nature of thisbinder strip necessarily will be determined by the character of the shoein which it is to be used. For some purposes it will simply be a stripof rubber compound. In other shoes, such for example as that shown inFig. l, it is preferable to use a fabric binder of some such nature asthat illustrated in Fig. 5, the .color and texture of which willcontribute to the general design of the shoe. The tread layer d may bemade of any suitable rubber composition which will give the desiredwearing qualities. It also may be colored, embossed, or ornamented inany suitable manner. In making this shoe the usual procedure is to makeand stitch together the parts of the upper'in the usual manner, and thento perform the shoe making operations on a last, the 'various parts ofthe bottom having previously been manufactured. Usually the insole 3 isfirst secured to the bottom of the last, its margins are coated withcement, and the upper is lasted over upon these margins in the samemanner as in making rubber footwear of the orthodox types. Next a rubberwelt 6 is cemented entirely around the lower margin of the insole 3, anda friction binder sheet 'l is cemented to the bottom of the insole,provided this strip has not been included in the insole: structure. Inthe latter event, it is coated with cement at this stage oi' theprocess. The sisal fiber assembly c now is properly registered with theedges of the shoe andl is laid upon the bottom of the insole and theoverlasted margins of the upper, after which the tread layer d issimilarly registered with and applied to the bottom of the section c. Ifthe parts have been assembled while the rubber elements are in anunvulcanized condition, then the shoe will be subjected tovulcanization. n the other hand, if the parts when assembled are in avulcanized or self-vulcanizing state, then the vulcanizing step may beeliminated. Usually the former practice is preferred. While the sisalsection of the outsole may be made in various ways, the preferred methodconsists in working the long sisal fibers into the form of a layer orsheeted body having considerable thickness, say for example,three-eighths of an inch or a half inch. such a body is illustrated atIll in Fig. 6. This operation can be performed by hand or in variouskinds or ber working machinery designed for the purpose of manipulatingfibers and presenting them in a sheeted or bat form. In such a, sheetedbody the fibers are not arranged inany definite relationship to eachother, but are disposed promiscuously, the fibers being so distributed,however, that when the mass is compressed a sheet or layer ofsubstantially uniform thickness will be produced. In this connection itmay be pointed out that while sisal is the preferred ber, hemp can alsobe used satisfactorily. The textile bers and others of a similar nature,however, are distinctly inferior. The sheeted stock produced in themanner. above described is next impregnated with a binder adapted tobond the fibers together permanently. lA flexible waterproof bindershould be used for this purpose and the best material which I have beenable to i'lnd is a rubber binder such as rubber latex, either vulcanizedor unvulcanized. In some cases, however, other binders, such as those ofan asphaltic nature, or those made from synthetic gums, resins, orbalsams, may be employed. The impregnating step may be performed in anyconvenient manner as. for example, by running the sisal ber bat throughthe liquid binder and then through squeeze rolls to remove the surplus,after which the bat should be dried to evaporate the solvent or otherdispersing agent used. If latex is used for this purpose in the ordinaryconcentrations, the bat will pick up approximately its own weight' ofrubber. In other words, after the water or serum has been evaporated,the impregnated sheet will have gained approximately its own weight ofdry rubber. The proportion of binder so`added to the bat can, however,be controlled by suitably varying the concentration of the impregnatedbath.

The impregnating, squeezing, and drying operations above describedcompresses the bat so that its nal thickness may be perhaps one-quarteror one-half of that of the original bat. The material at this stage ofthe process is indicated at Il in Fig. 7. Usually it is desirable toapply a calendar coat of rubber to one side of the sheet ll, as shown atI2 in Fig. 8, and for most purposes a spreader coat I3 of rubber issubsequently applied to the uncoated side f the sheet.

In making insoles a sheet of the material which is to form the uppersurface of the insole may then be combined with the layer shown in Fig.8. Also,in these calendaring and spreader coating operations the layeris further consolidated to bring it down to the desired dimensions, thefinal thickness being so predetermined that the layer will have thenecessary degree of mechanical strength, porosity and resistance tocompression.

The sheeted layer of sisal fiber produced in the manner above describedis a highlyporous, open, reticulated structure through which air flowsvery freely, the proportion of binder added to the original fiber beingso limited-.that the fibers are united chiefly at their intersectionswith each other, but the interstitial spaces are not substantiallyreduced. In this connection it may be pointed out that in making theinsole 3 the layer Il, as shown in Fig. 7, is sometimes used.

In making soles or heels several processes may be followed. For example,the' uncoated but impregnated layers l I may be completely filled withrubber and either vulcanized, or partially vulcanized, depending uponthe subsequent shoe making processes. At any convenient stage in thisprocedure the plies may be secured together to produce soles and heelsof the desired thickness as illustrated at 8 and 9 on the shoe shown inFig. 9. Here the soles and heels are solid, but a high proportion of therubber has been displaced by sisal ber and the presence of these fibersat the bottom or wearing surfaces of these members greatly reices thetendency of the rubber to slip on a wet surface.

According to the method usually preferred, the sisal layers Il arecoated on one or -both sides and then the desired number of them aresuperposed, one on another, necessary to build up a structure of therequired thickness for the heel or sole (both these elements beinghereinafter included, where the context permits, in the term outsole).Sole and heel blanks may be cut out of such an assembly with the usualcutting dies, and the heel blanks may be applied to the heel ends oi'the sole blanks, as shown in Fig. 10,

the sole blank being indicated at Il and the heel blank at I5. Theseparts will be secured to each other by the rubber coating or coatingswhich they carry. Subsequently a tread layer I6 of a suitable rubbercomposition is applied to the outer Cil surface of this entire assemblyand secured thereto by the inherent adhesiveness of these parts or bysuitable rubber cement. Also, an edge covering or binding strip I1 ofrubber preferably is applied to this whole assembly, this strip beingcut to size and shaped preparatory to being applied, one edge f, Fig.11, being registered with the inclined breast of the heel portion of theoutsole and then the strip being extended around the heel and theforepart and the nal edge g abutted against the edge f. 'I'his binderoverlaps both the sisal and the rubber plies and is folded over upon theupper surface of the sisal section I4, as clearly shown in Fig. 12.

'I'he outsole assembly produced in the manner just described is thenready to be applied to the bottom of such a shoe as that shown, forexample, in both Figs. 9 and 15. The latter shoe is of the outing type,usually made with a fabric upper, and the upper and outsole are securedtogether partly by the union of the rubber constituents of the insoleand outsole and partly through the medium of a welt strip I8 like thatshown at 6 in Figs. 1 to 4. During the vulcanizing operation this weltbonds securely to or unites with the folded-over portion of the coverstrip I1 on the upper surface of the outsole assembly and these twoparts thus cooperate to form a continuous rubber member unitingthe-tread ply I6 of rubber with-the upper of the shoe. Thus all theexposed surfaces of thesisal body are completely covered with rubber.

Sections of the shoe shown in Figt 15 are illustrated in Figs. 16 and17, the upper being indicated at 2D and the insole at 2I. A sisal llerstrip 22 may or may not be used, as desired.

In some cases it is preferable to run the tread strip I6 for the soledirectly through the heel and then to mount the heel on top of thisstrip. Such an arrangement is illustrated in Fig. 18 where the sisallayer is shown at I4' and the tread layer of the sole at I6', thislatter layer extending the entire length of the sole. T he heel includesa sisal section I', a tread section 23 of rubber, and an edge coveringstrip 24 also of rubber. In this arrangement, therefore, the sisal bodyI5 is completely enclosed at top, bottom and sides by rubber. Preferablya stiifer sheet of material I9, Figs. 10 and 14, loaded with rubber isplaced at the bottom of the heel above the tread layers I5 or I6 whereit serves to reinforce the tread layer.

It should be observed that in all these shoes .a` high proportion of thevolume of the bottom structure consists of sisal ber. Consequently,

such a shoe may be made extremely light in weight while still havingexceptionally good heatinsulating properties, ample resiliency to givethe cushioning properties which are one of the important advantages ofrubber shoes, and while body of air immediately under the foot, and alimited amount of interchange of this air naturally occurs in walkingdue to the resiliency of the sisal structure, better ventilation for thefoot is produced than in ordinary shoes, and the tendency to burn thebottoms of the feet or to make them sweat excessively, is obviated. Infact, the shoe is extremely cool in hot weather. The shoe bottom alsohas the same wearing and waterproof characteristics as prior rubbersoled shoes of corresponding types. vMoreover the sisal layers are ofadvantage in imparting to the sole added strength and the degree ofstiness necessary to counteract the excessive exibility of the rubber.In addition, the expense of manufacture of a shoe of this character isless than that of shoes of corresponding grades made by the usual rubbershoe methods.

Having thus described my invention, what I desire to claim as new is:

1. A shoe comprising an upper, an insole, and a rubber tread memberunited thereto, a high percentage of the volume of said tread memberconsisting of a layer of sisal fibers loosely matted together butsecured to each other by a exible binder, the proportions of saidbinderbeing so limited that said layer maintains a relatively thick bodyof air under the foot, and a rubber connection between lthe tread memberand the shoe upper.

`2. A shoe comprising an upper, an insole, and an outsole unitedthereto, said outsole comprising a relatively thick layer of sisalfibers loosely matted together but secured to each other by a ilexiblewaterproof binder, the proportions of said binder being so limited lthat said layer maintains a relatively thick body of air under the foot,a rubber tread layer permanently secured to said sisal layer, and arubber connection between the tread layer and the shoe upper.

` 3. A shoe comprising an upper, an insole, and an outsole unitedthereto. said outsole comprising a relatively thick layer of sisal bersloosely matted together but secured to each other by a-ilexible binder,the proportions of said binder being so limited that said layermaintains a relatively thick body of air under the foot, a rubber treadlayer permanently secured to said sisal layer, and a rubber stripcovering the edge of said sisal layer and united with said rubber layerand connected to the shoe upper.

4. A shoe comprising an upper, an insole, and an outsole united thereto,said outsole comprising a relatively thick layer of sisal iibers looselymatted together but secured to each other by a ilexible waterproofbinder, the proportions of said binder being so limited that said layermaintains a relatively thick body of air under the foot, a rubber treadlayer permanently secured to said sisal layer, a rubber strip coveringthe edge o! said sisal layer -and united with said rubber layer, and arubber welt strip connecting said edge covering strip with the upper o!the shoe.

ERNEST W. DUNBAR.

